Key Publications
Using a sophisticated Monte Carlo simulation-based cross-correlation technique on month-long X-ray light curve from RXTE/PCA and 1.5 month-long UV continuum light curves from IUE spectra in 1220-1970 Å, we found a remarkable switch from the slow comptonisation delay to the fast X-ray reprocessing delay between UV and X-rays.
Using X-ray spectral and timing analysis of the transient black hole X-ray binary 4U 1630-47, observed with the AstroSat, Chandra, and MAXI space missions during its soft X-ray outburst in 2016, we determine the dimensionless black hole spin parameter at 0.92 ± 0.04 within the 99.7% confidence interval. Such a measurement implies the central black hole is rotating close to its theoretical maximum limit.
Using a 2-day long X-ray monitoring with AstroSat and Radio monitoring with RATAN, we catch the rare moment when the relativistic radio jet base formed and ejected from the X-ray binary system known as Cyg X-3. Within a hour, the radio flux increases by a factor of ~5 and a very flat and strong Sychrotron emission appeared in the hard X-rays. Such a discovery provides first direct evidence of hard X-ray emission from the radio jet base.
Key Journels
The Astrophysical Journal (ApJ; IF 5.58)
ApJ LETTERS (IF 8.37)
Monthly Notices of Royal Astronomical Society (MNRAS; IF 5.231)
MNRAS LETTERS (IF 5.42)
Nuclear Instrumentations and Methods in Physics Research Section A (IF 1.4)
Journal of High Energy Astrophysics (IF 10.5)
Journal of Astronomy & Astrophysics (JAA)
Nature Astronomy (IF 14.5)
Collaborators
Mondal, A. S., Pahari, M., and Dewangan, G. C., “NuSTAR discovers a long type-I X-ray burst from the clocked burster GS 1826-24”, Journal of High Energy Astrophysics, vol. 49, Art. no. 100450, Elsevier, 2026. https://www.sciencedirect.com/science/article/pii/S2214404825001314
Baruah, A. and Pahari, M., “UV Flux Variation Study in Contact Binary VW Cephei”, Research in Astronomy and Astrophysics, vol. 25, no. 10, Art. no. 105013, IOP, 2025. doi:10.1088/1674-4527/adf9da.
Chatterjee, K., “Distinct Fe K Line Complexes in MAXI J1744‑294 Revealed by XRISM High-resolution Spectroscopy”, The Astrophysical Journal, vol. 992, no. 2, Art. no. 210, IOP, 2025. doi:10.3847/1538-4357/ae07d8.
Bagchi, M., “Astrophysics with compact objects: An Indian perspective, present status and future vision”, Journal of Astrophysics and Astronomy, vol. 46, no. 2, Art. no. 62, Springer, 2025. doi:10.1007/s12036-025-10077-5.
Dewangan, G. C., “Supermassive black holes and active galactic nuclei”, Journal of Astrophysics and Astronomy, vol. 46, no. 2, Art. no. 60, Springer, 2025. doi:10.1007/s12036-025-10075-7.
Sethuram, R., “New age observing facilities for Indian astronomy: 2020–2035”, Journal of Astrophysics and Astronomy, vol. 46, no. 1, Art. no. 25, Springer, 2025. doi:10.1007/s12036-025-10047-x.
Mondal, A. S., Bhattacharya, M., Pahari, M., Raychaudhuri, B., Ghosh, R., and Dewangan, G. C., “NuSTAR view of the X-ray transients Swift J174805.3-244637 and IGR J17511-3057”, Journal of High Energy Astrophysics, vol. 45, Elsevier, pp. 359–370, 2025. doi:10.1016/j.jheap.2025.01.005.
Sarkar, A. and Pahari, M., “Effect of magnetic field on the formation of radiatively inefficient accretion flow around black holes”, Physical Review D, vol. 111, no. 2, Art. no. 023008, APS, 2025. doi:10.1103/PhysRevD.111.023008.
Dutta, T., Pahari, M., Sarkar, A., Bhattacharyya, S., and Bhargava, Y., “Probing the origin of the extended flaring branch of Z-type X-ray binaries GX 340+0 and GX 5-1 using AstroSat”, Monthly Notices of the Royal Astronomical Society, vol. 535, no. 4, OUP, pp. 3383–3395, 2024. doi:10.1093/mnras/stae2529.
Bhattacharya, M., Mondal, A. S., Pahari, M., Raychaudhuri, B., Ghosh, R., and Dewangan, G. C., “Relativistic X-ray reflection from the accreting millisecond X-ray pulsar IGR J17498-2921”, Monthly Notices of the Royal Astronomical Society, vol. 534, no. 1, OUP, pp. 634–644, 2024. doi:10.1093/mnras/stae2135.
Pahari, M., “AstroSat and NICER timing view of the Z-type neutron star X-ray binary GX 340 + 0”, Monthly Notices of the Royal Astronomical Society, vol. 528, no. 3, OUP, pp. 4125–4138, 2024. doi:10.1093/mnras/stae309.
Bhargava, Y., Bhattacharyya, S., Homan, J., and Pahari, M., “AstroSat View of the Neutron Star Low-mass X-Ray Binary GX 340+0”, The Astrophysical Journal, vol. 955, no. 2, Art. no. 102, IOP, 2023. doi:10.3847/1538-4357/acee7a.
Vincentelli, F. M., Beard, M., Hardy, I. M., Cackett, E., Horne, K., and Pahari, M., “The evolution of the UV /optical lag spectrum of NGC 7469 seen by the Liverpool Telescope”, Astronomische Nachrichten, vol. 344, no. 4, Art. no. e20230018, Wiley, 2023. doi:10.1002/asna.20230018.
Beard, M. W. J., “Time-scale-dependent X-ray to UV time lags of NGC 4593 using high-intensity XMM-Newton observations with Swift and AstroSat”, Monthly Notices of the Royal Astronomical Society, vol. 519, no. 1, OUP, pp. 91–101, 2023. doi:10.1093/mnras/stac3391.
Castro Segura, N., “A persistent ultraviolet outflow from an accreting neutron star binary transient”, Nature, vol. 603, no. 7899, pp. 52–57, 2022. doi:10.1038/s41586-021-04324-2.
Williams, D. R. A., “LeMMINGs - IV. The X-ray properties of a statistically complete sample of the nuclei in active and inactive galaxies from the Palomar sample”, Monthly Notices of the Royal Astronomical Society, vol. 510, no. 4, OUP, pp. 4909–4928, 2022. doi:10.1093/mnras/stab3310.
Baldi, R. D., “LeMMINGs III. The e-MERLIN legacy survey of the Palomar sample: exploring the origin of nuclear radio emission in active and inactive galaxies through the [O III] - radio connection”, Monthly Notices of the Royal Astronomical Society, vol. 508, no. 2, OUP, pp. 2019–2038, 2021. doi:10.1093/mnras/stab2613.
Yadav, J. S., Agrawal, P. C., Misra, R., Roy, J., Pahari, M., and Manchanda, R. K., “LAXPC instrument onboard AstroSat: Five exciting years of new scientific results specially on X-ray binaries”, Journal of Astrophysics and Astronomy, vol. 42, no. 2, Art. no. 40, Springer, 2021. doi:10.1007/s12036-021-09717-3.
Antia, H. M., “Large Area X-ray Proportional Counter (LAXPC) in orbit performance: Calibration, background, analysis software”, Journal of Astrophysics and Astronomy, vol. 42, no. 2, Art. no. 32, Springer, 2021. doi:10.1007/s12036-021-09712-8.
Vincentelli, F. M., “On the multiwavelength variability of Mrk 110: two components acting at different time-scales”, Monthly Notices of the Royal Astronomical Society, vol. 504, no. 3, OUP, pp. 4337–4353, 2021. doi:10.1093/mnras/stab1033.
N. Castro Segura, C. Knigge, J. A. Acosta-Pulido, D. Altamirano, S. del Palacio, J.V. Hernandez Santisteban, Pahari, M., P. Rodriguez-Gil, C. Belardi, D.A.H. Buckley, M.R. Burleigh, M. Childress, R.P. Fender, D.M. Hewitt, D.J. James, R.B. Kuhn, N.P.M. Kuin, J. Pepper, A.A. Ponomareva, M.L. Pretorius, J.E. Rodríguez, K.G. Stassun, D.R.A. Williams, P.A. Woudt 2021, MNRAS, Link: https://arxiv.org/pdf/2008.07462.pdf : Bow-shocks, nova shells, disc winds and tilted discs: The Nova-Like V341 Ara Has It All
Pahari, M., McHardy, I. M., Vincentelli, F., Cackett, E., Peterson, B. M., Goad, M., Gultekin, K., Horne, K. 2020, MNRAS, 494, 4057: Link: https://ui.adsabs.harvard.edu/abs/2020MNRAS.494.4057P : Evidence for variability time-scale dependent UV/X-ray delay in Seyfert 1 AGN NGC 7469
Vincentelli, F. M., Mastroserio, G., McHardy, I. M., Ingram, A., Pahari, M., 2020, MNRAS, 492, 1135: Link: https://ui.adsabs.harvard.edu/abs/2020MNRAS.492.1135V : X-ray reverberation lags from the 1.5 Seyfert galaxy NGC 5273
D. R. A. Williams, McHardy, I. M., Baldi, R. D., Beswick, R. J., Pahari, M., Argo, M. K., Beri, A. et al., 2019, MNRAS, 486, 4962: Link: https://ui.adsabs.harvard.edu/abs/2019MNRAS.486.4962W : Unveiling the 100 pc scale nuclear radio structure of NGC 6217 with e-MERLIN and the VLA
Beri, Aru, Paul, Biswajit, Yadav, J. S., Antia, H. M., Agrawal, P. C., Manchanda, R. K., Dedhia, Dhiraj, Chauhan, Jai Verdhan, Pahari, M., Misra, Ranjeev, et al. 2019, MNRAS, 482, 4397: Link: https://ui.adsabs.harvard.edu/abs/2019MNRAS.482.4397B : Thermonuclear X-ray bursts in rapid succession in 4U 1636-536 with AstroSat-LAXPC
Roy, J., Agrawal, P. C., Iyer, N. K., Bhattacharya, D., Yadav, J. S., Antia, H. M., Chauhan, J. V., Choudhury, M., Dedhia, D. K., Katoch, T., Madhavani, P., Manchanda, R. K., Misra, R., Pahari, M., Paul, B., and Shah, P. 2019, ApJ, 872, 33: Link: https://ui.adsabs.harvard.edu/abs/2019ApJ...872...33R : LAXPC/AstroSat Study of ~1 and ~2 mHz Quasi-periodic Oscillations in the Be/X-Ray Binary 4U 0115+63 during Its 2015 Outburst
Rawat, Divya, Pahari, M., Yadav, J. S., Jain, Pankaj, Misra, Ranjeev et al. 2019, ApJ, 870, 4: Link: https://ui.adsabs.harvard.edu/abs/2019ApJ...870....4R : Study of Timing Evolution from Nonvariable to Structured Large-amplitude Variability Transition in GRS 1915 + 105 Using AstroSat
McHardy, I. M., Connolly, S. D., Horne, K., Cackett, E. M., Gelbord, J., Peterson, B. M., Pahari, M., Gehrels, N., et al., 2018, MNRAS, 480, 2881: Link: https://ui.adsabs.harvard.edu/abs/2018MNRAS.480.2881M : X-ray/UV/optical variability of NGC 4593 with Swift: reprocessing of X-rays by an extended reprocessor
Pahari, M., Bhattacharyya, S., Rao, A. R., Bhattacharya, D, et al. 2018, ApJ, 867, 86 : Link: https://ui.adsabs.harvard.edu/abs/2018ApJ...867...86P : AstroSat and Chandra View of the High Soft State of 4U 1630-47 (4U 1630-472): Evidence of the Disk Wind and a Rapidly Spinning Black Hole
Mondal, Aditya S., Dewangan, G. C., Pahari, M., and Raychaudhuri, B. 2018, MNRAS, 474, 2064: Link: https://ui.adsabs.harvard.edu/abs/2018MNRAS.474.2064M : NuSTAR view of the Z-type neutron star low-mass X-ray binary Cygnus X-2
Pahari, M., Yadav, J. S., Verdhan Chauhan, Jai, Rawat, Divya, et al., 2018, ApJ Letters, 853, 11 : Link: https://ui.adsabs.harvard.edu/abs/2018ApJ...853L..11P : Extensive Broadband X-Ray Monitoring During the Formation of a Giant Radio Jet Base in Cyg X-3 with AstroSat
Pahari, M., Antia, H. M., Yadav, J. S., et al. 2017, ApJ, 849, 16: Link: https://ui.adsabs.harvard.edu/abs/2017ApJ...849...16P : X-Ray Timing Analysis of Cyg X-3 Using AstroSat/LAXPC: Detection of Milli-hertz Quasi-periodic Oscillations during the Flaring Hard X-Ray State
Gandhi, P., Bachetti, M., Dhillon, V. S., Fender, R. P., Hardy, L. K., Harrison, F. A., Littlefair, S. P., Malzac, J., Markoff, S., Marsh, T. R., Mooley, K., Stern, D., Tomsick, J. A., Walton, D. J., Casella, P., Vincentelli, F., Altamirano, D., Casares, J., Ceccobello, C., Charles, P. A., Ferrigno, C., Hynes, R. I., Knigge, C., Kuulkers, E., Pahari, M., et al. 2017, Nature Astronomy, 1, 859 : Link: https://ui.adsabs.harvard.edu/abs/2017NatAs...1..859G : An elevation of 0.1 light-seconds for the optical jet base in an accreting Galactic black hole system
Pahari, M., McHardy, I. M., Mallick, L., Dewangan, G. C., and Misra, R. 2017, MNRAS, 470, 3239: Link: https://ui.adsabs.harvard.edu/abs/2017MNRAS.470.3239P : Detection of the high-energy cut-off from the Seyfert 1.5 galaxy NGC 5273
Pahari, M., Gandhi, Poshak, Charles, Philip A., Kotze, Marissa M., Altamirano, D. and Misra, Ranjeev 2017, MNRAS, 469, 193: Link: https://ui.adsabs.harvard.edu/abs/2017MNRAS.469..193P : Simultaneous optical/X-ray study of GS 1354-64 (=BW Cir) during hard outburst: evidence for optical cyclo-synchrotron emission from the hot accretion flow
Antia, H. M., Yadav, J. S., Agrawal, P. C., Verdhan Chauhan, Jai, Manchanda, R. K., Chitnis, Varsha, Paul, Biswajit, Dedhia, Dhiraj, Shah, Parag, Gujar, V. M., Katoch, Tilak, Kurhade, V. N., Madhwani, Pankaj, Manojkumar, T. K., Nikam, V. A., Pandya, A. S., Parmar, J. V., Pawar, D., M., Pahari, M., Misra, Ranjeev, et al., 2017, ApJS, 231, 10 : Link: https://ui.adsabs.harvard.edu/abs/2017ApJS..231...10A : Calibration of the Large Area X-Ray Proportional Counter (LAXPC) Instrument on board AstroSat
Court, J. M. C., Altamirano, D., Pereyra, M., Boon, C. M., Yamaoka, K., Belloni, T., Wijnands, R., and Pahari, M. 2017, MNRAS, 468, 4748: Link: https://ui.adsabs.harvard.edu/abs/2017MNRAS.468.4748C : An atlas of exotic variability in IGR J17091-3624: a comparison with GRS 1915+105
Verdhan Chauhan, Jai, Yadav, J. S., Misra, Ranjeev, Agrawal, P. C., Antia, H. M., Pahari, M., Sridhar, Navin, et al. 2017, ApJ, 841, 41: Link: https://ui.adsabs.harvard.edu/abs/2017ApJ...841...41V : AstroSat/LAXPC Detection of Millisecond Phenomena in 4U 1728-34
Mallick, Labani, Dewangan, Gulab C., McHardy, I. M., & Pahari, M., 2017, MNRAS, 472, 174: Link: https://ui.adsabs.harvard.edu/abs/2017MNRAS.472..174M : Energy-dependent variability of the bare Seyfert 1 galaxy Ark 120
Mondal, Aditya S., Pahari, M., Dewangan, G. C., Misra, R., and Raychaudhuri, B. 2017, MNRAS, 466, 4991: Link: https://ui.adsabs.harvard.edu/abs/2017MNRAS.466.4991M : NuSTAR and Swift joint view of neutron star X-ray binary 4U 1728-34: disc reflection in the island and lower banana states
Misra, Ranjeev, Yadav, J. S., Verdhan Chauhan, Jai, Agrawal, P. C., Antia, H. M., Pahari, M., Chitnis, V. R., Dedhia, Dhiraj, et al. 2017, ApJ, 835, 195 : Link: https://ui.adsabs.harvard.edu/abs/2017ApJ...835..195M : AstroSat/LAXPC Observation of Cygnus X-1 in the Hard State
Gandhi, P., Littlefair, S. P., Hardy, L. K., Dhillon, V. S., Marsh, T. R., Shaw, A. W., Altamirano, D., Caballero-Garcia, M. D., Casares, J., Casella, P., Castro-Tirado, A. J., Charles, P. A., Dallilar, Y., Eikenberry, S., Fender, R. P., Hynes, R. I., Knigge, C., Kuulkers, E., Mooley, K., Munoz-Darias, T., Pahari, M., Rahoui, F., et al. 2016, MNRAS, 459, 554: Link: https://ui.adsabs.harvard.edu/abs/2016MNRAS.459..554G : Furiously fast and red: sub-second optical flaring in V404 Cyg during the 2015 outburst peak
Yadav, J. S., Misra, Ranjeev, Verdhan Chauhan, Jai, Agrawal, P. C., Antia, H. M., Pahari, M., Dedhia, Dhiraj, et al. 2016, ApJ, 833, 27: Link: https://ui.adsabs.harvard.edu/abs/2016ApJ...833...27Y : Astrosat/LAXPC Reveals the High-energy Variability of GRS 1915+105 in the chi Class
Mondal, Aditya S., Dewangan, G. C., Pahari, M., Misra, R., Kembhavi, A. K., Raychaudhuri, B. 2016, MNRAS, 461, 191: Link: https://ui.adsabs.harvard.edu/abs/2016MNRAS.461.1917M : Broad-band X-ray emission and the reality of the broad iron line from the neutron star-white dwarf X-ray binary 4U 1820-30
Mir, Mubashir Hamid, Misra, Ranjeev, Pahari, M., Iqbal, Naseer, Ahmad, Naveel 2016, MNRAS, 457, 2999: Link: https://ui.adsabs.harvard.edu/abs/2016MNRAS.457.2999M : A model for the energy-dependent time-lag and rms of the heartbeat oscillations in GRS 1915+105
Pahari, M., Misra, Ranjeev, Dewangan, Gulab C., and Pawar, Pramod 2015, ApJ, 814, 158: Link: https://ui.adsabs.harvard.edu/abs/2015ApJ...814..158P : Constraining Distance and Inclination Angle of V4641 Sgr Using Swift and NuSTAR Observations during Low Soft Spectral State
Pahari, M., Yadav, J. S., and Bhattacharyya, Sudip 2014, ApJ, 783, 141: Link: https://ui.adsabs.harvard.edu/abs/2014ApJ...783..141P : X-Ray Spectral State Evolution in IGR J17091-3624 and Comparison of its Heartbeat Oscillation Properties with those of GRS 1915+105
Pahari, M., Misra, Ranjeev, Mukherjee, Arunava, Yadav, J. S., and Pandey, S. K. 2013, MNRAS, 436, 2334: Link: https://ui.adsabs.harvard.edu/abs/2013MNRAS.436.2334P : Interpreting the large amplitude X-ray variation of GRS 1915+105 and IGR J17091-3624 as modulations of an accretion disc
Pahari, M., Neilsen, Joseph, Yadav, J. S., Misra, Ranjeev, & Uttley, Phil 2013, ApJ, 778, 136 Link: https://ui.adsabs.harvard.edu/abs/2013ApJ...778..136P : Comparison of Time/Phase Lags in the Hard State and Plateau State of GRS 1915+105
Pahari, M., Yadav, J. S., Rodriguez, J., Misra, Ranjeev, Bhattacharyya, Sudip, and Pandey, S. K. 2013, ApJ, 778, 46 : Link: https://ui.adsabs.harvard.edu/abs/2013ApJ...778...46P : Properties of Unique Hard X-Ray Dips Observed from GRS 1915+105 and IGR J17091-3624 and Their Implications
Pahari, M. and Pal, S. 2012, MNRAS, 423, 3352 : Link: https://ui.adsabs.harvard.edu/abs/2012MNRAS.423.3352P : RXTE observation of recent flaring activity from the transient X-ray pulsar 2S 1553-542
Pahari, M., Bhattacharyya, Sudip, Yadav, J. S., AND Pandey, S. K. 2012, MNRAS Letters, 422, 87 : Link: https://ui.adsabs.harvard.edu/abs/2012MNRAS.422L..87P : Evidence of two unique variability classes from IGR J17091-3624
Pahari, M. and Pal, Sabyasachi 2010, MNRAS, 409, 903: Link: https://ui.adsabs.harvard.edu/abs/2010MNRAS.409..903P : Signature of long-term class evolution in GRS 1915+105 at a high accretion rate
Pahari, M., Yadav, J. S., Mishra, Suprabha A., and Pandya, A., 2010, NIMPA, 621, 364: Link: https://ui.adsabs.harvard.edu/abs/2010NIMPA.621..364P : Large area high temperature hard X-ray spectroscopy detectors for space experiments
Selected non-refereed Publication
Yadav, J. S., Agrawal, P. C., Antia, H. M., Chauhan, Jai Verdhan, Dedhia, D., K., Tilak, M., P., Manchanda, R. K., Misra, R., Pahari, M., et al., 2016, Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray :Link: https://ui.adsabs.harvard.edu/abs/2016SPIE.9905E..1DY : Large Area X-ray Proportional Counter (LAXPC) instrument onboard ASTROSAT
Pahari, M., Singh Yadav, J., Antia, H. M., and Misra, R. 2016, 41st COSPAR Scientific Assembly : Link: https://ui.adsabs.harvard.edu/abs/2016cosp...41E1495P : ASTROSAT/LAXPC observations of X-Ray binaries: A new window to hard X-Ray science aspects
Yadav, J. S. And Pahari, M. 2011, Astronomical Society of India Conference Series: Link: https://ui.adsabs.harvard.edu/abs/2011ASInC...3..136Y : Stable X-ray states in X-ray black hole binaries
Pahari, M., Bhattacharyya, S., and Yadav, J. S. 2011, The Astronomer's Telegram, 1 Link: https://ui.adsabs.harvard.edu/abs/2011ATel.3667....1P : Black hole X-ray binary IGR J17091-3624 shows a unique intensity variation pattern
Pahari, M., Pal, S. and Mukherjee, A. 2010, The Astronomer's Telegram, 1 : Link: https://ui.adsabs.harvard.edu/abs/2010ATel.2902....1P : RXTE/PCA detection of QPO near 0.22 Hz in Aql X-1 during ongoing outburst